In the monkey, the first apparent sign of the absorption of Cobra-venom, or of the venom of any other species of Colubridæ, is a sort of general lassitude; the eyelids next become half closed. The animal appears to be seeking a suitable spot in which to rest; it gets up again immediately, and walks with a jerky action; its limbs have a difficulty in supporting it. It is soon attacked by nausea, vomiting and dyspnœa; it rests its head upon the ground, raises it, trying to get breath, and carries its hand to its mouth as if in order to pluck a foreign body from its throat. It totters upon its limbs, and lies down upon its side with its face against the ground. Ptosis increases, and complete asphyxia soon supervenes. The heart continues to beat for some time after respiration has ceased, and then stops in diastole.
Cadaveric rigidity very rapidly sets in, and persists for a long time, even after putrefaction has commenced. During the last moments of life the pupil remains very sensitive; the animal appears to retain unimpaired its sense of hearing and sensibility to pain. The electric excitability of the muscles of the face persists, but that of those of the limbs and body almost entirely disappears. The application of volta-faradic currents from the nape to the diaphragm produces no respiratory movement when asphyxia begins to manifest itself. The sphincters of the bladder and anus relax after a few spasms, which, in case of males, frequently provoke the ejaculation of semen; the urine and fæces immediately escape.
The autopsy reveals slight hæmorrhagic œdema at the point of inoculation, and hyperæmia of all the viscera, especially of the liver and spleen, with, very frequently, small hæmorrhagic patches on the surface of these organs, and on that of the intestine and kidneys. The serous membranes, especially the meninges, endocardium, pleuræ, and peritoneum, exhibit ecchymoses; the lungs are besprinkled with small infarcts, the more numerous the slower the intoxication. The blood remains fluid and laccate.
In poisoning by the venoms of Viperidæ, the hæmorrhagic phenomena appear at the outset, and are more intense. Death is always preceded by a period of asphyxia, indicating that the bulbar nuclei of the pneumogastric nerve have become affected. At the autopsy, however, the blood, instead of remaining fluid, is always found to be coagulated into a mass in all the vessels; it afterwards gradually becomes redissolved in six or eight hours, and then appears laccate, as after poisoning by Cobra-venom, but darker.
All mammals exhibit the same symptoms after inoculation with lethal doses of venom. The same applies to birds; but in the latter the period of asphyxia is much longer, probably on account of the reserves of air accumulated in their air-sacs and pneumatic bones. They gape like pigeons that are being suffocated, rest the tip of the beak on the floor of the cage, and frequently have convulsive spasms of the pharynx, accompanied by flapping of the wings. Small birds and even pigeons are extremely sensitive to venom; fowls are more resistant.
Frogs, thanks to their cutaneous respiration, succumb very slowly. I have seen some survive for thirty hours after being inoculated with a quantity of venom which, when subcutaneously injected into a rabbit, causes death in ten minutes.
Lizards and chameleons succumb very rapidly. Grass Snakes and non-venomous snakes in general withstand doses of venom that in proportion to their weight are fairly large; nevertheless, as indeed we shall see in the sequel, they do not possess any real immunity. It is only poisonous snakes that are unaffected by enormous doses of their own venom, as has already been shown by Fontana, Weir Mitchell, and Viaud Grand Marais. They are, however, quite capable of being poisoned by snakes belonging to altogether different species; strong doses of Crotalus- or Lachesis-venom are fatal to Cobras or Kraits, and, when several poisonous snakes are shut up together in the same cage, they are not infrequently seen to kill each other as the result of repeated bites.